The present invention relates to an installation for and a method of rolling a continuous cast strip and, more particularly, to a rolling installation and a rolling method suitable for rolling a thin slab cast strip cast by a continuous casting machine, to reduce a width of the strip without cutting the same.
Conventionally, a system is known in which a sheet-like thin slab cast strip cast by a continuous casting machine is hot-rolled, without cutting the cast strip, to produce a hot-rolled strip, from the viewpoint of energy saving and improvement of the yield. However, such system have numerous problems in regulating width-reduction rolling of the strip. That is, if the thin slab cast strip is rolled to be reduced in width while the cast strip is hot, buckling and deformation occur in the the cast strip widthwise thereof. Thus, in practice, it is almost impossible to regulate the strip width.
Japanese Patent Application Laid-Open Nos. 60-87903 and 55-133803 disclose width-reduction rolling techniques for such thin slabs.
In the technique disclosed in Japanese Patent Application Laid-Open No. 60-87903, a continuous casting machine of double-drum type is employed, and a vertical width-reduction rolling mill is arranged upstream of a thickness-reduction rolling mill. The arrangement is such that a thin slab cast strip cast by the continuous casting machine of a double-drum type is rolled to be reduced in strip width by the vertical rolling mill, thereby regulating the strip width.
In the technique proposed in Japanese Patent Application Laid-Open No. 55-133803, a width-reduction rolling mill is arranged between a pair of thickness-reduction rolling mills. At width-reduction rolling, respective portions of a thin slab cast strip in front of and in rear of the width-reduction rolling mill are restrained respectively by the thickness-reduction rolling mills, to thereby prevent the cast strip from being buckled and deformed widthwise of the cast strip.
The thin slab cast strip delivered from the continuous casting machine is relatively wide. For example, the strip thickness is 20 to 40 mm, while the strip width is 600 to 1600 mm. By this reason, when the cast strip is compressed widthwise thereof by the vertical rolls in accordance with the proposal described in Japanese Patent Application Laid-Open No. 60-87903, buckling at once occurs in the cast strip. Thus, it has been found that the method disclosed in this Japanese patent does not effectively regulate of the strip width.
On the other hand, in the proposal described in Japanese Patent Application Laid-Open No. 55-133803, the respective portions of the thin slab cast strip in front of and in rear of the width-reduction rolling mill are restrained respectively by the thickness-reduction rolling mills. It has been likewise impossible, however, to obtain sufficient effects of regulation of the strip width with this method. That is, the rolls of the actual width-reduction rolling mill are equal to or larger than 600 mm in diameter, and the rolls of each of the thickness-reduction rolling mills are also equal to or larger than 600 mm. Accordingly, even if the number of the rolls width-reduction rolling mill is not three pairs as is in the above Japanese patent, but is reduced to a single pair, a distance between the respective thickness-reduction roll pairs in front of and in rear of the width-reduction rolling mill is to a large value, such as 600.times.2=1200 mm. As a result, it becomes impossible to sufficiently restrain the cast strip widthwise thereof by the thickness-reduction roll pairs. Thus, there is little effect on prevention of widthwise deformation at the width-reduction rolling.